| In the context of global climate change,the increasing loss of biodiversity has triggered a global wave of research on the relationship between biodiversity and ecosystem function.Biodiversity enhances the ability of ecosystems to maintain multiple functions,such as carbon storage,productivity,and nutrient pool accumulation.However,in natural ecosystems,most previous studies have been limited to the relationship between diversity at a single level of plant communities or microbial communities and ecosystem multifunctionality(EMF),and few studies have focused on the link between biodiversity and EMF at both above-ground(plants)and below-ground(soil microbes)levels combined.Desert steppe ecosystems are extremely fragile and sensitive to climate change.Therefore,it is important to investigate the effects of precipitation changes on biodiversity and ecosystem functions in desert steppes for the restoration of degraded steppes and ecologically sustainable management.In this study,five precipitation gradients,33%,66%,100%(CK),133%and 166%of natural precipitation(corresponding to 106 mm,212 mm,321 mm,427 mm,and 533 mm of precipitation,respectively),were simulated using a rain shelter device and artificial water replenishment techniques for field precipitation control experiments in the Ningxia desert steppe.By studying plant species diversity,soil microbial diversity and eight ecosystem function indicators closely related to ecosystem productivity and carbon and nitrogen storage in desert steppe ecosystems,we aim to reveal the response patterns of above-ground and below-ground community diversity and ecosystem function of desert steppe ecosystems to changes in precipitation,and analyze the above-ground and below-ground biodiversity of desert steppe to ecosystem multifunctionality under changes in precipitation.The main findings are as follows:(1)Precipitation changes significantly affected plant diversity in the desert grassland.533 mm precipitation treatments significantly increased species richness(SR)and species density,106 mm precipitation treatments significantly decreased SR and species density,while 212 mm and 427 mm precipitation treatments did not significantly affect SR and density.The positive effect of increasing precipitation on SR and species density was greater than the negative effect of decreasing precipitation on SR and species density.(2)Precipitation changes did not significantly alter the bacterial community composition and its diversity.The main phyla of the soil bacterial community under different precipitation changes included Actinobacteria(41.5%),Proteobacteria(17.7%),and Chloroflexi(15.7%).Precipitation significantly altered the fungal Chao 1 index,decreasing by 35.2%under 427 mm precipitation.The main phyla of soil fungal communities under different precipitation changes included Ascomycota(79.9%),Basidiomycota(8.7%),and Mortierellomycota(4.5%);precipitation treatments did not significantly affect the Shannon-Wiener diversity index of bacteria and fungi,but the ShannonWiener diversity index of bacteria and fungi was not significantly affected.There was no significant effect of precipitation treatment on Shannon-Wiener diversity indices of bacteria and fungi,but the response ratio of Shannon-Wiener diversity indices of bacteria showed a decreasing trend with precipitation.(3)Precipitation changes significantly affected the functional indicators of desert steppe ecosystems.The response ratios of aboveground biomass(AGB),aboveground carbon stock(AGCS),belowground carbon stock(BGCS),aboveground nitrogen stock(AGNS),and belowground nitrogen stock(BGNS)was significantly and linearly correlated with precipitation.533 mm precipitation treatment significantly increased the mean ecosystem multifunctionality(EMF),and increasing precipitation treatment increased the EMF at different thresholds(10%,25%,50%,75%,and 90%).However,the negative effect of water reduction treatment on EMF was greater than the positive effect of water increase treatment on EMF.The response ratios of ecosystem multifunctionality for different thresholds were significantly and positively correlated with the amount of precipitation.(4)Under different precipitation treatments,EMF was significantly linearly positively correlated with species diversity,while it was significantly linearly negatively correlated with bacterial diversity,but the changes in EMF were not significantly related to fungal diversity.the results of Mantel test showed that plant diversity was significantly correlated with AGB,AGCS,AGNS,BGCS and BGNS,respectively;bacterial diversity was significantly correlated with AGB,AGCS and AGNS,respectively;while fungal diversity was not significantly correlated with any of the ecosystem function indicators.Changes in precipitation affect the feedback effects of plant diversity on above-ground plant communities and their carbon and nitrogen stocks thereby indirectly affecting soil microbial communities,ultimately driving the relationship between species diversity and bacterial diversity and ecosystem multifunctionality.When soil abiotic factors were included,random forest and path analysis models indicated that precipitation drove the interrelationship between above-and belowground biodiversity and ecosystem function by influencing biotic and soil abiotic factors,with biotic and abiotic factors together explaining 69%of the variability in ecosystem multifunctionality.In summary,changes in precipitation affect the regulation of plant diversity on bacterial diversity by altering the effectiveness of water and nutrients,resulting in a stronger coupling between above-ground and below-ground biodiversity and ecosystem multifunctionality.Although plant diversity and microbial diversity play an important role in driving ecosystem functions,plant diversity may be more important for predicting changes in desert steppe ecosystem functions,which is of great significance for biodiversity conservation and ecosystem stability in desert steppe. |
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